Astronomers discover abundance of rare metals on Jupiter-sized exoplanet that rains iron

This illustration shows a night-side view of the exoplanet WASP-76 b where molten iron condenses and forms iron droplets. Credit: ESO/M. Kornmesser

A team of international astronomers have found abundance of rare metals (found in Sun) on hot Jupiter-like exoplanet WASP-76b using the Gemini North telescope, as per the findings of their study published in the Nature journal.

The temperature on this planet rises up to 4,350 degrees Fahrenheit (2,400 degrees Celsius), hot enough to vaporize iron.

The exoplanet is around 634 light years away in Pisces constellation, and is classified under "ultra hot giant" planets that are incredibly close to their star. WASP-76b is twelve times as close to its star as Mercury is to Sun.

"Truly rare are the times when an exoplanet hundreds of light years away can teach us something that would otherwise likely be impossible to know about our own solar system," Stefan Pelletier, team leader and PhD student at Université de Montréal Trottier Institute for Research on Exoplanets said in a statement, as reported by Space.com. "This is the case with this study."

WASP -76b was found in the Wide Angle Search for Planets (WASP) programme 2013 and has been a subject for intense study.

WASP-76b, like the Moon, is tidally locked, with one side of the planet permanently facing the host star. This leads to a temperature difference between the ‘day side’ - facing the host star- and the ‘night side’- facing the space. The astronomers estimated that it is over 2,400 degrees Celsius on the day side and about 1,500 degrees Celsius on the night side.

The temperature difference can lead to strong winds wherein the molten iron from the day side of the planet condenses towards the night side and rains iron.

Pelletier and team decided to observe the planet with the MAROON-X high-resolution optical spectrograph on the Gemini North 8-meter Telescope in Hawaii, part of the International Gemini Observatory, which allowed the study to be conducted in unprecedented detail.

The high temperature of WASP-76b meant that the elements were found in the upper atmosphere, unlike in cold planets like Jupiter where they are in lower atmosphere making them impossible to detect.

Pelletier and team found abundance of elements like manganese, chromium, magnesium, vanadium, barium, and calcium matching with amount present in its host star as well as the Sun. This research was published in Nature on June 14.

The composition of terrestrial planets like Earth is different due the complex process of formation. But the abundance of the elements in WASP-76b being comparable to the abundance in all stars suggests that it is the same in all gas giants.

They also found vanadium oxide in the planet’s atmosphere. Pelletier explained in Space.com, "This molecule plays a similar role to ozone in Earth's atmosphere: it is extremely efficient at heating up the upper atmosphere. This causes the temperatures to increase as a function of altitude, instead of decreasing as is typically seen on colder planets."

The research also shows high abundance of nickel hinting that at some point in time WASP-76b might have swallowed Mercury-like planet rich in nickel.